Waffle Slab Research Articles

Sustainability of column‐supported slabs for buildings: A multi‐criteria assessment

AbstractThe global construction industry is experiencing significant growth, driving the demand for building floor area. However, this expansion comes with substantial environmental consequences, including high‐energy consumption and greenhouse gas (GHG) emissions, together with economic and social impacts. To address these challenges, this research aims at providing designers and decisions‐makers with an approach that will aid the quantification of those impacts relevant for the sustainability performance of flooring systems. A holistic sustainability assessment was performed considering economic, environmental, and social aspects using the Integrated Value Model for Sustainability Evaluations. This study focused on various flooring typologies, including reinforced concrete (RC) and fiber‐RC (FRC) slabs with solid and waffle (for RC solution) configurations. The most representative criteria and indicators of sustainability for concrete column‐supported slabs were identified, measured, and weighted—aggregated in a decision‐making tree—in order to obtain a representative a sustainability index (SI) for each alternative. The results of the analysis evidence that the RC solid slab has a higher overall SI than the other alternatives, the FRC alternatives performing with similar SI of that quantified for the RC solid slab solution and the RC waffle slab being that with the lower sustainability performance among those flooring systems considered in this study. The results of a sensitivity analysis showed that those alternatives using FRC have potential for improving the overall sustainability performance.

Experimental Study of Punching Shear on Reinforced Concrete Waffle Slabs Strengthened by CFRP Sheets

Experimental Study of Punching Shear on Reinforced Concrete Waffle Slabs Strengthened by CFRP Sheets

Structural analysis for a slab-on-grade cellular concrete foundation to reduce heat losses in temperate climate residential buildings

Reducing the energy requirements of buildings is imperative in the face of global warming and the imminent need to build low or zero-carbon housing in the following decades. This research proposes the design of a structural foundation to reduce heat transfer between the ground and the house to improve thermal comfort, thus reducing the incidence of low interior temperatures and lower energy requirements. The proposed foundation consists of a waffle slab system incorporating on-site cellular concrete fabrication for a residential home. The foundation proposal was evaluated over a year through simulation to quantify the heating demand reduction for four cities with temperate semi-arid and temperate sub-humid climates. The analysis shows that the prevalence of low temperatures is reduced when applying any of the proposed foundations. However, the benefits must be weighed for cities like Durango and Puebla since the reduction of hours with low temperatures is minimal, and they show an increase in energy for cooling. The city with the most significant benefit in reducing the incidence of low temperatures and the heating demand is Toluca, followed by Zacatecas, which are cities showing prevalent heating demands. Based on the results, it is observed that it is viable to apply foundations with a lower overall heat transfer coefficient, with the addition of lightened materials produced on-site. However, it is still necessary to conduct more experimental studies on these prefabricated systems applied to foundation slabs and care for their implementation in mixed climates.

Parametric study on the decarbonization potential of structural system and concrete mix design choices for mid-rise concrete buildings

Mid-rise reinforced concrete buildings are projected to continue being the predominant typology for urban development. Thus, reducing the carbon footprint of such buildings is critical for achieving a sustainable built environment. Reducing the amount of concrete and steel in a building through structural and mix design optimization is identified as a primary resource efficiency strategy. This paper is among the first to present evidence of the decarbonization potential of these dematerialization strategies on a building level. The study combines structural design choices such as slab system design, steel reinforcement optimization and span width with materials-based strategies, such as low binder concrete and low-carbon binders. For each scenario, material quantities are calculated following design prescriptions by EN1992–1–1 while state-of-the art life cycle inventory data are adopted to calculate the carbon footprint. Results show that shifting towards more efficient structural systems (i.e., waffle slab system) could save up to 20% of the carbon footprint on the building level compared to more traditional systems, such as slab on beams and flat slabs. In addition, reducing the spans from 7.5 to 5 m can save up to 20% more. Finally, the use of low-clinker cement in low-binder concrete can save another 50% in terms of CO2 impact per built-up area. Realistically, results of the case study concluded that implementing these three strategies could reduce the typical 232 kg CO2e/m2 value of the carbon footprint of structural elements of a mid-rise building up to only 58 kg CO2e/m2, i.e., a four-fold reduction.

Assessment of Large Span Multistory Building Using Various Slab Under Earthquake Response

With the growing need for multistory buildings in a variety of industries, the need for novel structural solutions has become critical. This research looks at the structural behaviour of wide span structures, with an emphasis on the use of various slab forms to meet the problems provided by growing architectural trends. The study undertakes a detailed literature analysis, looking into the use of Grid Slabs, Flat Slabs, Waffle Slabs, and Ribbed Slabs alongside regular slabs to improve stiffness and load-carrying capability in large-span buildings. Architects are challenged to accommodate bigger spans while minimising the number of columns, which has led to the introduction of novel slab layouts. Grid Slabs, which have unique grid patterns, and well-established Flat Slabs are popular alternatives. The analysis of the literature reveals an increasing trend among academics who have effectively used various slab designs to meet the issues given by long spans. The findings provide architects, structural engineers, and construction industry stakeholders significant insights into the performance features and advantages associated with each slab type. This study adds to the continuing discussion about optimising structural designs for large-span structures to meet the changing demands of current construction practises. The complete analysis is a helpful resource for professionals involved in multistory building design and construction, assisting in informed decision-making and supporting developments in the field.

Erratum for “Strength, Ductility, and Collapse Response of UHPC Waffle Slabs”

Erratum for “Strength, Ductility, and Collapse Response of UHPC Waffle Slabs”

Increasing the Vertical Load Capacity of Reinforced Concrete Waffle Slabs With Varying Operating Loads Using CFRP

Increasing the Vertical Load Capacity of Reinforced Concrete Waffle Slabs With Varying Operating Loads Using CFRP

Comparative Cost and Design of Solid, Ribbed and Waffle Slab for a Three-storey Shopping Complex Using Prota, Orion and Spreadsheet

Cost is an important factor in choosing the type of floor or slab used in any construction. When a large space within a building needs to be covered without hindrance and supports, waffle or ribbed slabs are used. For all slab systems, the cost constitutes a significant portion of the overall cost of the structure. Therefore, this research aims to select a preferable slab system with the least construction cost for a shopping mall. Computer-aided design software such as Prota 2018 and Orion 2018 was used for analysis and design, and RCC spreadsheets were used to manually check the slabs. The results reveal that the Solid floor slab has more concrete volume and steel than the waffle, and the rib consumes the lowest least volume of concrete and steel among the three slab systems. Therefore, the rib slab is the most economical of the three slab systems since it uses the least concrete and reinforcement. The cost of a floor slab system ranges from 12 to 17% of the structural cost in building works, the percentages of the cost of the slab in a floor system is 17.84% for solid slabs system, 13.65% for rib slabs and 12.48% for waffle slabs of the total cost of a structure. It can therefore be concluded that using rib slab saves 17.95% and 7.46% of the construction sum when compared to solid slab and waffle slab construction systems respectively. In conclusion, it is recommended that ribbed slabs should be used for commercial building construction with more than 5KN/m2 live load in commercial buildings that spans up to 15m and more.

Exploring Analytical Hierarchy Process for Multicriteria Assessment of Reinforced Concrete Slabs

The decision regarding which slab type should be used in a building is generally made by the structural engineer, considering structural efficiency and compatibility with the architectural design, as well as the costs related to the amount of material used in each option. Because of the technical responsibilities inherent to this specialty, the decision-making process neglects to encompass various other factors of consequence that influence the construction process. These considerations include productivity, the visual and aesthetic characteristics of the slab, waste generation, and thermal and acoustic comfort. This paper aims to develop a multicriteria method to assist stakeholders in selecting the most suitable structural system for slabs based on project needs and objectives. The study utilized the Analytic Hierarchy Process (AHP) and information from bibliographic research, expert opinion using the Delphi Method, and machine learning on a dataset of over 2000 previously constructed slabs to achieve this goal. The analysis showed that the conventional solid slab type was the top priority, followed by the two-way waffle slab, one-way waffle slab, solid flat slab, and waffle slab. Additionally, the proposed AHP method was effective in developing a decision-making model for companies and the construction sector.

Building energy and exergy analysis of the light-weight roofs compared with the traditional ones in different climates

A significant research gap exists concerning the thermal properties of lightweight roofs, as extensive investigations have predominantly focused on their mechanical characteristics. However, there is a notable dearth of studies addressing the thermal behavior of lightweight roof systems. The comprehension of thermal properties in lightweight roofs is of paramount importance, as it enables the promotion of energy-efficient design practices. The absence of comprehensive research in this domain constrains the optimization of thermal insulation mechanisms within lightweight roof constructions. Consequently, this hinders developments aimed at reducing energy consumption in buildings. To bridge this research gap, this study investigates the thermal performance of two lightweight roofs called waffle slab and bubble deck in three different climates, and compare them with conventional cement block roofs. Results revealed that Valencia had the lowest heating load due to its moderate climate, while Denver showed the minimum cooling load due to colder temperatures. The bubble deck roof outperformed other roofs in terms of heat loss reduction, achieving an average of 76% in winter and 41% in summer. Additionally, the bubble deck roof demonstrated the best overall efficiency (72% on average) and improved thermal comfort during summer, with lower energy consumption. Exergy analysis showed that the bubble deck roof significantly reduced input and output exergy, indicating its superior energy conservation capabilities compared to waffle slab and cement block roofs. These findings emphasize the potential benefits of lightweight roofs, particularly the bubble deck, in enhancing energy efficiency and occupant comfort.

Punching Shear Design of Waffle Slabs at Internal Column Connections

Punching Shear Design of Waffle Slabs at Internal Column Connections

Effects of Slab Types on the Seismic Behavior and Construction Cost of RC Buildings

Reinforced concrete-framed buildings are commonly preferred to other types of buildings in Turkey. In these types of buildings, a two-way slab with beams, flat, waffle, and ribbed slab types are widely used. In building design, determining the best slab type that will perform well under gravity and lateral loads, with the least cost, is required. However, the proper selection of slab type has generally been overlooked by designers due to the emphasis on other structural members, such as beams, columns and structural walls. For this reason, the structural contribution of floors to building design has not been adequately examined. This shortcoming must be inspected in detail starting from the very first step of the design stage of a building. This study assesses the effects of different slab types on multi-story reinforced concrete buildings by investigating their structural behaviors while trying to optimize their overall cost. For this purpose, a total of 36 structural models were constructed, analyzed, and designed according to the current Turkish Building Codes and Standards. The type of slab system (a two-way slab with beams, flat, waffle and ribbed), the number of floors (10, 20 and 30), and span length (6, 7.5, and 9 m) were selected as the key parameters in these analyses. The buildings were assumed to be office buildings located in a seismically-active zone in Istanbul. The results indicated that a two-way slab with beams was the most economical slab type for 6-meter spans, while the waffle slab was the most economical for spans larger than 7.5 meters. Based on these results, the flat slab was found to be the most expensive slab type in all cases. Out of all slab types, the two-way slab with beams exhibited better earthquake performance, while the waffle and flat slabs provided relatively poor earthquake performances.

Strength, Ductility, and Collapse Response of UHPC Waffle Slabs

Waffle slabs made of ultra-high performance concrete (UHPC) are now being widely used in bridge deck construction. However, to date, no research has been conducted to study their failure behavior. Two one-way waffle slab strips made of UHPC were load-tested under four-point bending to investigate their strength, ductility, and failure patterns. An identical set made of high strength concrete (HSC) was also tested to provide a comparison to specimens made with traditional construction materials. The UHPC specimens exhibited multiple fine cracks prior to rebar yielding and failed by steel rebar rupture after a single crack localized. In contrast, the HSC slab strips exhibited several large cracks and substantially larger ductility than the UHPC slab strips, although their strength was about 40% less than the corresponding UHPC specimens. The experimental results were used to validate a three-dimensional finite element model, which was then employed to investigate the two-way response of UHPC waffle slabs. The simulation study revealed that the yield line design method is applicable to UHPC waffle slabs despite their markedly different behavior compared to concrete slabs. Like the HSC slabs, the UHPC slabs also exhibited displacements and load carrying capacities well in excess of those predicted by flexural theories, due to formation of membrane action.

SCAD model of solid finite elements: calculation of reinforced concrete waffle slabs

Introduction. Current requirements for structural engineering oblige designers to use structures capable of resisting progressive collapse. Such structures include multiribbed reinforced concrete waffle slabs. Spatial systems are multiple indeterminate, their calculation is carried out in software systems based on the finite element method. Models of ribbed structures can be developed from different types of finite elements. The forces determined by different models can vary significantly, which is confirmed by the examples available in the literature.Aim. To detect a simple and accurate finite element model for computer-aided calculating the ribbed reinforced concrete waffle slab.Materials and methods. The study was carried out by comparing the bending moments obtained analytically and in the SCAD software by the finite element method for beams in waffle slabs of 12.0 × 18.0 m in plan with caissons of 1.5 × 2.25 m. The bar model consisting of a T-beam-and-girder construction and a solid model of bulk finite elements are calculated.Results. The bending moments, calculated both analytically and using a solid model, have similar values. The maximum deviations of the computer calculation from the analytical method are from -3.2 to +2.6 %. The maximum deviations of the values of bending moments obtained when comparing the solid model with the bar model are from -9.2 to +4.0 %.Conclusion. The finite element model, which is based on solving the volumetric problem of the elastic theory, is an effective verification model for studying complex systems; however, it is time-consuming and difficult for data analysis. A solid model can be recommended for studying individual structures or their critical zones.

Condition Assessment and Seismic Evaluation of High Rise Building Having Pylons on Outer Periphery and Central Core Tube System Connected With Waffle Slab

An existing structure has to have its condition assessed primarily to determine whether it still meets the requirements for serviceability and safety. Continuously monitoring concrete structures can be done more effectively using NDT technologies. As a result of recent earthquakes in the Indian many existing buildings need to undergo a seismic evaluation. This project work contains condition assessment of existing RCC framed structure through detailed visual inspection and preparation of distress mapping plan along with evaluation of in-situ strength of structural components using non destructive tests. Prepared structural drawings of existing building using state of art device. Also carried out seismic evaluation based on condition assessment using FEM based software (Etabs). Standard repair/strengthening methodologies against observed deficiencies are recommended.

EVALUATION OF STRUCTURE USING VARIETY OF SLAB TYPE UNDER PERFORMANCE-BASED DESIGN: CASE STUDY COMMON WORKING SPACE IN SURABAYA

Improvement of the current construction of midrise to high-rise building in Surabaya relatively needs to be evaluated, especially for compact office building area, it is very challenging to have an optimal space to the structural system with facilitate a satisfactory capacity performance. This paper makes a comparative study of the effectivity of structural plate structure in the compact office building between conventional slab (M1), waffle slab (M2) and flat slab (M3). A typical 5-story reinforced concrete building structure is selected as a case study within 6 m symmetrically span for each model. The proposed method used in this study is based on empirical analysis followed by numerical evaluation using SAP2000. The step initiated by deriving an optimal alternative of various type of slab. This study aims to emphasize the benefits to the functionality of the structural system which more efficient in term of structural capacity and its performance. As the result, M1 and M3 offer a similar behaviour due to the reinforcement and design performance with high slab deformation compared to the M2. M2 present a lower slab deflection under the supported of waffle element with the result almost twice smaller than M1 and M3.

Seismic Analysis of a Multi-Storey Building with Different Types of Slabs

Earthquake plays an influential role in the analysis and design of structures. Unless the structures are designed and constructed to withstand seismic forces, failure cannot be avoided. Buildings can be made seismically sound with proper structure design, detailing and construction practice. The configuration of a building is very much important for the seismic performance of buildings. The important aspects that affect the seismic configuration of a building are overall geometry and structural system. This parameter varies in their behaviour in the flat slab, waffle slab and conventional slab. Therefore introducing different types of slabs becomes very crucial for a structural engineer when it comes to better performance of RC structure. The objective of this paper is to study the seismic behaviour of multi-storeyed buildings with different types of slab systems. The study is done by considering the varying number of stories i.e. low-rise, mid-rise and high-rise buildings. The study aims to find an effective slab system for both regular and irregular structures. The different types of slabs considered are flat plate system, flat slab with drop system and waffle slab system which is compared with the conventional slab system. Seismic assessment using response spectrum analysis is done. For low-rise to high-rise buildings, the seismic behaviour of the waffle slab is more effective.

ВЕРИФИКАЦИЯ СТЕРЖНЕВОЙ И ТВЕРДОТЕЛЬНОЙ МОДЕЛЕЙ ВЫЧИСЛИТЕЛЬНОГО КОМПЛЕКСА SCAD РАСЧЕТА ЖЕЛЕЗОБЕТОННОГО КЕССОННОГО ПЕРЕКРЫТИЯ

In accordance with modern requirements for the design of buildings, designers are needed to use structural solutions that are resistant to progressive collapse. A space-working caisson-type overlap is one of such solutions. Spatial constructions are repeatedly statically indeterminate systems and their calculation is performed on a computer in software complexes based on the finite element method. A ribbed model can be created from various types of finite elements and get data that varies. One of the ways to control the finite element method is to calculate structures using different models. The purpose of the work is to search for the simplest and most accurate finite element model for calculating a ribbed reinforced concrete waffle slabs. The work is a continuation of verification studies of SCAD models for calculating reinforced concrete waffle slabs with a size of 9.0 x 11.55 m. The bending moments in the beams obtained by the analytical method using a rod model and a model created from three-dimensional elements are compared. The values of bending moments calculated analytically and using a solid-state model have similar values. The maximum deviations of the FEM from the analytical method of calculation are from -0.9 to +11.6%. The values of bending moments calculated using a solid-state model and a rod model have similar values. The maximum deviations range from -9.7 to +6.3%. The finite element model, the calculation of which is based on solving the volumetric problem of elasticity theory, is effective, but time-consuming to create and difficult to analyze the data obtained.

Engineering design of optimized reinforced concrete floor grillages

A new reinforced concrete beam grillage floor system is proposed as a lightweight alternative to traditional solid flat or waffle slabs used in construction. For the first time, beam grillage optimization has been paired with design code compliant floor plate design, for single and multi-bays of a building. The investigated floor slabs are novel, in that the depths of the grillage T-beams and their reinforcement are tailored for the local strength demands. This engineering efficiency gives rise to significant savings of approximately 40–50% in the quantities of concrete and steel needed compared to flat slabs. For the multi-bay studies, it was found that moving the location of the supporting columns could further decrease the volume of material required, by over 50% compared to a standard grid layout. Given the urgent need to reduce the volume of material consumed in construction projects, this appears to challenge traditional floorplate layouts. The research shows that digital optimization tools can be paired with standard design code rules to deliver significantly more sustainable building designs, though these benefits need to be balanced against the construction challenges associated with the more complex geometries that generally result.

Comparative analysis and design of solid ribbed and waffle slabs for residential buildings: A review

Comparative analysis and design of solid ribbed and waffle slabs for residential buildings: A review